Ljania Thor, 1898

Tuzovskij, Petr V., 2012, Water mites of the genus Ljania Thor, 1898 (Acari: Hydrachnidia: Aturidae) in Russia, Zootaxa 3249, pp. 1-17 : 2-3

Genus Ljania Thor, 1898

Diagnosis. Adults. Idiosoma flattened dorsoventrally. Dorsal and ventral shields separate. Formula of idiosomal setation is 2–2–4–4–6–4–4–4–2–4–0. Trichobothria Fp, Oi and setae Sci, Li, Si, Ci and Pi usually without glandularia, but in L. japonica Imamura, 1956 and L. michiganensis Cook, 1974 Si associated with glandularia. Dorsal shield very large, covering nearly all dorsal surface ( Fig. 24 ) and bearing 6 pairs of setae: Oi, Oe, Hi, Sci, Li, Si; Oe, Hi and Li located along to lateral margins of dorsal shield, Si near distal end of shield, with or without glandularia. Setae Fp, Oi, Sci, Li, Ci and Pi without glandularia, other idiosomal setae associated with glandularia. Setae He and two pairs of slit organs (i2, i 3) located on soft interscutal membrane: i2 posterolaterally to setae Oe, i 3 anterolaterally to setae Hi; Vi and first pair of slit organs (i1) located on anterior end of ventral shield dorsally; Oe slightly longer than other dorsal setae. Setae Fch and Fp placed on ventral shield anteriorly, but concealed by the anterior coxal plates; Hv located near posterior margin of Cx–II, Ve posterolaterally to prominent ridges, and Sce near posterior end of ventral shield; other ventral idiosoma setae arranged in soft integument. Seta and glandularium Le placed on tubercle, base of Se located close to this tubercle; bases of Ci and Pi separated or located on small common sclerite on each side, i5 situated laterally to Ci. Excretory pore on small platelet. Capitulum slightly elongate, with short anchoral process.

All coxal plates fused to one group, together with posteroventral sclerotization forming a large ventral shield, but medial suture lines of Cx-IV remaining well visible. Genital field with three pairs of acetabula, acetabular plates fused to ventral shield in males (with rather numerous setae) but separate in females (with several setae). A prominent ridge present on each side extending anterolaterally from insertions of legs IV. Cx-IV more or less projecting posteriorly, indented posteromedially, associated with seta and glandularium Pe near indentation. Excretory pore lying on a prominent tubercle dorsally or ventrally. Legs without sexual dimorphism, true swimming setae absent, leg claws with two clawlets.

Pedipalps rather slender. P–1 short, with a single dorsodistal seta; P–2 expanded distally, with straight ventral margin, 3 unequal dorsoproximal and 2 subequal dorsodistal setae; P–3 with slightly concave ventral margin, bearing 2 dorsoproximal and 2 dorsodistal setae, P–4 longer than P–2, with straight ventral margin and convex dorsal margin, bearing a single very short distolateral spine, 5 to 10 fine dorsolateral setae and 2 ventral setae; P–5 short and curved, with single long proximal solenidion, 4 unequal distal spines and 4 fine setae.

For chaetotaxy and proportions of I-Leg respectively IV-Leg see Figs 13 and 14 . I-Leg ( Fig. 5 ) noticeable longer than II-Leg. I–Leg–1–3 with several thick setae each; I–Leg–4–5 with thin setae only; I–Leg–6 bearing several unequal thin setae and several distal solenidia, second ventroproximal seta considerably longer than others ventral setae. Posterior pair of legs ( Fig. 6 ) with large trochanter bearing two thick dorsodistal setae; following four segments with several thick unequal setae each, IV–Leg–6 with 3 ventral spines and several thin setae. Claws of all legs ( Figs 7–8 ) with two unequal clawlets, claw lamella elongate with slightly concave ventral margin; claws of first pair of legs ( Fig. 7 ) shorter than claws of other legs ( Fig. 8 ).

Deutonymph. Idiosoma similar to adults differing in smaller size, shape of external structures of the genital area, and shape and size of dorsal and ventral shields. Dorsal shield relatively small, bearing three pairs of setae (Oi, Oe and Hi); Hv and Pe placed on ventral shield, other idiosomal setae located in soft integument. Coxal plates in three groups. Genital field with two small plates bearing 2 acetabula and 3 setae each, with single very small genital sclerite situated between these plates, gonopore absent. Number of setae on pedipalp and leg segments minor than in adult mites.

Larva. Dorsal plate and coxal plate with reticulation; coxal plates I separate, plate III without projections posteriorly, without transverse muscle attachment scars, bearing 1 pair setae, C4 anteriorly; excretory pore plate broadly obcordate and occupying nearly entire region posterior to coxal plates III, bearing 2 pairs of setae or, rarely, 3 pairs of setae; pedipalpal tarsus bearing 7 setae and 1 solenidion ( Smith 1984).

Larvae of the genus Ljania are known to parasitize the abdominal region of imagines of the family Chironomidae of the subfamilies Diamesiinae, Orthocladiinae and Chironominae ( Efford 1963, 1966; Smith 1984; Martin 2000; Martin & Stur 2006).

Figures

FIGURES 24 – 25. Ljania orientalis sp. n., male: 24 — dorsal view, 25 — ventral view. Scale bar: 24 – 25 = 100 μm.

FIGURES 12 – 15. Ljania macilenta Koenike, deutonymph: 12 — pedipalp, 13 — leg I, 14 — leg IV, 15 — claw. Scale bars: 12 = 20 μm, 13 - 14 = 50 μm, 15 = 25 μm.

FIGURES 3 – 8. Ljania macilenta Koenike, female: 3 - chelicera, 4 — pedipalp, lateral view, 5 — Leg I, 6 — leg IV, 7 — claw of leg I, 8 — claw of leg IV. Scale bars: 3 – 4 = 20 μm, 5 – 6 = 50 μm, 7 – 8 = 25 μm.